schwarz



y April 28, 1953 I H'. G. SCHWARZ; l

' v PULSE TYPE Poma SUPPLY.

' File@ Dec. 1s.. 1949 l H. G. SCHWARZ EULSE TYPE Pom SUPPLY pn'i 28,A1953 Filed Dec. 1s.I 1949 f myn/TOR.

HANS G. scmaakz @K4/WQ A ORNE s .2,265,620 to Bahring, No. 2,074,495 toVance, and

I .Application Bceeinber i6, 194,9. Serial No. 133,354

i 2 claims. (ci. 3er- 2) Y i The present invention relates toimprovements in high voltage power supply systems for televisionreceivers. I'here are fou'x` types of supply systems in general use:

' First, that which is based on step-up transformation andrectication ofthe 60 cycle alterhating current. supply, and modied forms involving theuse of voltage multipliers, as described at pages 158.164, Grob, BasicTelevision, Principlesand Servicing, McGraw-Hill Book Company.

' Inc., New York, 1949;

Second, the R. F. type, wherein a rectier is l energized by a.high-frequency oscillator, as described in the article entitledTelevision High Voltage R. F. Supplies vby M -autner and Schade. RCAReview, March i947, vol. VIII, No. pp. 43-8l, R. C. 'A. LaboratoriesDivision, Princeton. New Jersey, and also at pp. 164-168 of theaboiecited book by Grob;

Third, the ily-back type, `wherein energy is obtained by rectificationfrom the inductive circuit provided for horizontal scanning, as described at pages 168-170 of Grobs book and in U. S. Patent- No.2,051,372 to Farnsworth, No.

No. 2,218,764 to Moller and Behring;

Fourth, the pulse-type, as described in the ar- ,Patented `Apr.2.8,.1-953A f Nuntreu dstares; Pareri s631011 rfULsE-Trrnrowen SUPPLY li .l ,i

G'. Schwarz, Cincinnati, Ohio, assigner to y 'Aveo ManufacturingCorporation, tncinnafi, v Oho,a corporation of Delaware ticle entitledPulse-Type High-Voltage Supply,"

Siezen and Kerkhof, Proceedings of the Institute oi Radio Engineers,March 1948, pp. li0l407.

The advantages, disadvantages, and limitations of the various types oftelevision receiver power supply systems are known to the art and arediscussed in the literature, particularly in the pat-V ents andpublicationscited above. Among the. primary desirable attributes of apower supply l system are: (1) A high voltage D. C. output,

which ranges from as low as two kilovolts for some types of directlyviewed tubes to kilovolts or higher for projection tubes; (2) lowaverage current output, ranging from 100 to 200 microamperes; (3) lightweight; (4) small size; (5) minimum' shock hazard; (6) good powerefciency; (7) minimum nonsynchronous R. F. interierence; (8) inexpensiveltering circuits.

These requirements often dictate the use of a 'pulse-type' power supplyin specific designs, most frequently in projection type receivers.Constant pressure has been on those working in the art to obtain ahigher voltage output per unit based on the periodic interruption o!acurrent the high voltage of the't-ransient oscillation induced by thisreaction is rectied and filtered. Each interruption of current nowisfollowed by' 'a train of damped oscillations which occur duringdissipation of energy and substantially corn'V plete collapse ,of thestored power, Then the magnetic iield is completely built up again andthe cycle is repeated. Further, only the peaks of the rst cycle of thedamped transient oscillation areA rectified and the available highvoltage current is low since the total time during which peaks occur issmall by comparison to the time of each series oi damped oscillations.The primary object of the present invention is to effect a. radicalincrease :in efiiciency by .maintaining most of the magnetic energywithin'the system eindje-- creasing the number of useless cycles of theperiodically recurring oscillations.

accordance with' the invention the natural frequency of `the transformercircuit is so related to the repetition rate of the interruptions ofcurrent in the transformez-,circuit and to the time during which thepower tube is conducting that the time for one or only a few completecycles of the fundamental frequency of the transformerl output voltageplus the time of each' increment of cnn-ent required -to reach peakcurrent in the plate inductanceis equal to the reciprocal of the drivingpulso frequency.

A pulse-type power supply in accordance with i the invention comprises4an energy source. an irlductance which is periodically charged by thatsource, means including a switching tube for peicdically interruptingthe new of current in said induetance, thereby causingr the magneticfield to collapse, whereby there appears across said inductance anoscillatory voltage, means for peakcally recurring applied increments ofcurrent in said inductance are initiated at times when the oscillatorycurrent in the last-mentioned circuit is near or at its peak value andof 'the same polarity as those increments.

I prefer that the distributed capacitance of an inductor be utilized asthe above-mentioned parallel capacitance. The frequencies involved aresuch that economies may oe effected in this manner. dispensing with the'provision of a separate capacitor. The explanation of the basic conceptof the invention may be simplified by drawing.an

'analogy between the conventional pulse-type power-.supply and thependulum. The pendulous weight has `its maximum kinetic energy at themld-point'of its swing. The inductance has its maximum energy at the endof' its charge."

The flow of' current into the inductance is terminatori at. thatinstant. It may be assumed, to

continue the analogy, that the manual operator .of the pendulum stopshis "push at the mid-4 .of the pendulous system' must be entirely builtup again in order to attain the maximum swing again. In the conventionaltype of pulse-type power' supply, the natural periodicity of theinduotor circuit (correspondingto the pendulum) and the repetition rateof the driving impulses (each correspondingY to a push ceasing at thelmid-point of swing after a previous cycle of natural oscillations hasceasedl.- are such that the part of the originally stored magneticenergy which is left after the rst cycle, i. e., which is not used forthe high-voltage rectification, is

2,637,011 a j I known prior art type of power supply as well as to thepresent invention. This known typeot power supply comprises a sawtoothsignal generator, a power amplier l for converting the sawtooth voltagesignals into periodically recur- 'ring sawtooth currents, an inductancei2 through stored in its magnetic ileld is at' a maximum.

completely dissipated between driving-impulses.l s

Only' the peak voltage portions of the irst oscillation are rectined andthe vfollowing amplitudes,

decreasing in accordance with a logarithmic i decrement, of the manysucceeding oscillations in each train, are such that these succeedingoscil-,

lations do not attain the threshold of rectificaf tion. The uselessoscillations comprise by far the Y' greater portion of the totalnumberof oscillations in each train. Magnetic energy is dissipated tothe point of lexhaustion during the time of these useless oscillations.The ratio 'of available high-voltage power to stored magneticenergy'isaccordingly low- I have found that the above-mentioned ratio'and the power em'ciency of a pulse-type power4 supply may be radicallyincreased by applying power to the inductance at a'. repetition ratewhich is comparable to the natural frequency of the inductive circuit,or by so predetermining the natural frequency that it is comparable tothe.

impulse'rate.

In my novel powecsupply. the number of oscillations between successiveimpulses is not a. substantial multiple of the number of appliedimpulses. In the prior art power supply, the number of uselesspower-dissipating oscillations is many times greater than the num-- berof applied pulses. 4

Continuing the analogy, .my improved power supply may be likened to apendulum in which an.

impulse is supplied in the correct phase at the mid-point of each swing,or perhaps every second 01' third swing. The prior art system may belikened to a. pendulum which uselessly swings many times and comes torest before a new impulse is applied. The analogy 'was drawn a.

posteriori for the purpose ofcxplaining the operation of the inventionand not a priori.

For a better understandingoi' the present in-l vention, together withother and further objects, advantages, and capabilities thereof,reference is made to the following description of the accompanyingdrawil'igl1 Fig. 1 of which illustrates in schematic form apulse-typepower supply system in accordance with the invention; and

Fig. 2 comprising a set of curves employed as an aid in describing theinvention.

The symbols employed in the schematic diagram o! Fig. 1 are those which`are applicable to a appropriate `'control which these currents flow,and an energy source H, included in series with the inductance I2 in theplate circuit of the power tube i 4 for furnishing the' energyrepresented by these currents. In the priorl art circuit the tube I4functions as a jswitc'hing tube and periodically closes or becomesnon-conductii'e in order-to interrupt the ilow ofcurrent in inductor i2.Each interruption occurs at' the peak of a. sawtooth wave of current in1n-l ductor I2 an at a time when. the ma gnetlc energy tinues afterrectification has occured. During the continued oscillation followingpeak rectiiicatiom: the residual energy'of the system is dissipated.

until it attains a. value close to zero. The in' 4vention, although itmay be represented by thesame symbols as the prior art power supply,operates on a.. distinct principle in that a. very sub- -stantial amountof stored energy is retained in the system between control signals. Inthe priorl a' art system'substantially all of the energy is dissipatedfollowing the termination of each controlling-sawtooth signal and beforethe beginning of the next controlling sawtooth signal. In a.

power supply in accordance with the presentin-v vention, on the otherhand. a substantial amount of energy remains in the system after 'thefirst control pulse has performed its function and at the instant whenthe second control pulse becomes effective. In the prior art system thepower amplier tube remains conductive, in re' sponse to each sawtoothcontrol signal, sutil--4 ciently long to cause the current in theinductance i2 to build up from zero to its peak value. In the systemprovidedby the invention, on the 'other hand, the intervals ofconductivity of the power am-piiiier tube are relatively very short because it remains open during each interval only suihciently long tofurnish an increment of curf rent from, a'substantial value(representative of the energy retained in the system) to a peak value.

In the new system provided by the invention, pulses as 'represented 'bycurve Y, Fig. 2, are employed to govern the op' eration of amplier tubei4. These control pulses are produced by a pulse generator i6 (shownonly in block form) such as a plate-coupled mul-4, tivibrator. Thecontrol pulses could also be produced by a pulse shaping network coupledto a' line or horizontal synchronizing system oi' the televisionreceiver. LSince such expcdients as signal generators, pulse shapingnetworks and honplate current cut-ofi potential, rendering tube ilnon-conductive, and that the portion of each pulse during the intervaltr-tv, for example. is

above cut-offend renders tube Il conductive. It will be seen from. theiollowlng'description and l. from. what has already' been mentioned thatthe intervals of conductivity of tube I4 in my System are relativelyvery short.

The control pulses are applied to the control 'electrode of tube I4through a suitable coupling network comprising capacitor Il and gridresistor I8. The cathode of tube I4 is grounded as shown. 1c win beunderstood that inductan'ce I2 is'shunted by a number of capacitanceparameters including its own distributed capacitance and the capacitanceof the auto-transformer sec ondary circuit as reflected b ack to theprimary. These parameters are collectively indicated by the referencenumeral I9. In accordance with the invention the parameters of nductanceI2 and capacitance IS are so determined that the magnetic energy in thesystem is not completely dissipated between successive increments ofcurrent in inductance I 2.

Each interruption of current in inductance I2 causes a transientoscillatory voltage to appear across the inductance (curve Z, Fig. 2).The peak of this voltage is stepped up by an autotransformer, theprimary of which comprisesin-v .ductance [Zand thel secondaryof whichcomprises series winding portions I2 and 20, wound:

on the same core. Across the secondary isconne'cted the seriescombination of a. diode 'rectiiler tube 2l and load 22 (generally theacceleratarea ABC being'enti'rely dispensed with in the Acircuitcomprising inductance I2` and capacitor I9. this -decrease being thefirst stage ofl a traning anode circuit of a cathode-ray picture tube.

not shown).` Across the load is a shunt nit-er capacitor 2.3. Thefilament 24 of diode 2I is provided with its own secondary windingV 254inductively coupled to the auto-transformer. The positive peak of thetransient oscillatory voltage isrectined bytubeZI. The rectifier circuitper se. that is, the elements 20, 2i, 25, 23, and 22,A are individuallyand collectively a part of the prior art.

Coming now to describe the operation of my improved pulse type powersupply, it will be assumed that tube I4 becomes conductive at ti'rne ti.As shown in curve X of Fig. 2, the plate current in tube Ii instantlyassumes a substantial value Ii. tube i4. the current supplied to theinductor by the tube increases alongr a sawtooth characteristic (curveX, Fig. 2), finally attaining a maximum value I2, and additional energyis stored Y in the magnetic neld of inductance I2 over and The abovethat which it possesses at instant t1. maximum current value is attainedat instant t2.

At thatinstant the control pulse applied to the During the interval ofconductivity of ti with a sawtooth characteristic, but on the contrary'is rapidly initiated at a value I1 (curve X, Fig. 2). This means thatthe time oi conductivity of tube I4 is4 short relative to the time whichwould be required to attain value I2, with a sawto'oth characteristicinitiated -at zero value. Since the time of conductivity of tube I 4 isa measure of the power eiliciency of the system, it will be seen thatthev invention radically improves lpower eiilciency, the area BCDE incurve W, Fig. 2, representing-the power applied during each period ofconductivity of tube I4, being much smaller than the area ADE, `which isrepresentative of applied power in prior art circuits, the

second cycle of` free oscillation.

a substantial current is nowing inthe inductance sient oscillation.v Attime t: .the current through the inductance an'd the magnetic iieldreach instantaneous values of zero (curve W) but attain their maximumrates of change. At time t:

the energy in circuit I2, i9 iS-stored in the el.ec.

trostatic neld and the voltage across tube I6 (curve Z) reaches itsAmaximum in a positive direction. The peak of this voltage is rectifiedby tube 2|.

Inthe priorfart type of power supply, the tram sient oscillations of thetype shown in curves W and Z (following t2 or 'power tube cut-oil areallowed to continue until all energy is dissipated from the system. T tis within the -teachings of the present invention to render tube I4conductive again at or about timetr-when the energy from theelectrostatic system has again been nverted into magneticenergy-'-i..e., at or near the 'end of the first cycle oi freeoscillation in the pulses, and the output voltage for a given pulserepetition rate is smaller than is the case when the natural frequencyis larger. output voltage requires a higher step-up ratio in theauto-transformer. I prefer to reducethis stepup ratio by rcnderinnr tubeI4 conductive again at time t-i. e., at or near the end of the Atinstant te I2. This current is representative of magnetic energyretained within the system and not lost. As soon as tube I4 becomesconductive, at instant ts, this current ilows through the anode-cathodecircuit' of the tube. The current through the inductance is againincreased between instants ta and t1. and input energy is supplied bythe tube during this interval. The cycle is then repeated. preferably,as indicated above, at horizontal line frequency.

.Thus it will be seen that the invention pro vides a pulse-type powersupply comprising an energy source II (which may be the usual 10'.:7voltage plate supply source of a television receiver), an nductance I2which is periodically charged by that source (the expression "charged"being employed to designate the development o! sawtooth currents), meansincluding a switchirig tube I4 for periodically interrupting the now oicurrent in the inductance. thereby causing the magnetic eld to begin tocollapse (between times t2 and t3, whereby there appears across saidnductance an oscillatory voltage (first peak in curve Z). means 2I forpeak-rectifying said volt age (at instant ta) to derive a unidirectionalvoltage, and a capacitance (which may be the distributed capacitanceIil) effectively in parallel with said inductance I2 to form a circuithav-- The lsmaller that this oscillatory current is of positive polarityat instants tz and4 te. 'and' that. the applied increases of currentrepresented by the curve X.

Fig. 2, are of positive polarity.. The invention.

' provides a system in which thev natural frequency.

of theoseillatory circuit I2.. I9 is such that. the timeior two completecyclesI (t1-ts) lot the. funisat. or near itspeal:I value. It will.alsobe seen.'

'agefwhich-isbulttunacrossinrluctur l2 during tire time. that; powertube .t4 is. conductive- As this voltage is very snail -compued tothe.transient oscillatory voltage (curve. Z, Fig. 2), it. is neg damentalfrequency of. the transformer output voltage plus the time required tobuild' up maxim'unr current in. the' plate. inductance (te-t7). is

equal to the reciprocal of the driving pulse fiequencytte., tv minustz.curvelhox: 1

' the pulse generator, in order to correlatethc pulse repetition rateand natural frequency of the oscillatory circuitV l2, i9. In the specicexample shown, the time for two complete cycles of the resonantfrequency plus the time necessaryto drive the plate inductance tomaximum current value is equal to the reciprocal oi the' driving pulsefrequency. V It is within thespirit oi the invcntion to make one. or.two or three -or a few complete cycles of the resonant frequency plusthe time necessary to drive the plate inductanceV t'o maximum currentvalue equal to lthe recipro.

cal of the line frequency, because the invention achieves useful resultsin minimizing the dissipation of magnetic energy from the system betweencontrol impulses. The invention becomes particularly useful from Vthestandpoint of iucreasing power. eiiiciency most economically when freeoscillation of the resonant system for two os-I cillations is permitted,as in the specic illustrativeembodiment herein described in detail.

It is particularly important. to note that at in,- stant t4, the end of.the iirst cycle of the transient oscillation, a substantial amount ofcurrent of' positive polarity is flowing in inductor |22 (curve W, Fig.2)'. It is within the teachings of the present invention to utilize.this current by opening tube i4 at an. instant corresponding to t4. andto supply an increment of current from Vtube i4 in order to build up thecurrent in inductor l2 to its peak value. Such a result could beaccomplishedL by making the natural frequency ot the circuit i2, i9apaproximately one-half ot the. natural frequency on which Fig. 2 isbased, relative. to, the. repetition. rate of the control pulses. Insuch case the natural frequency of the oscillatory circuit would be.such that the. time; required for one cycle of the oscillatory voltageplus the time required to build up maximum current in the plateinductance i2 would be equal to. the reciprocal of the driving pulsefrequency.

It will be understood that the curves of Fig, 2

i represent simplified conditions, and while they take intoconsideration those factors bearing on the merits of the presentinvention, certain negllgible factors are not reflected therein. Forexample, curve W is premised on the assumption that at instant tz. themoment of interruption` of the current in inductorl l2, the currentimmediately decreases along a sinusoidal characteristic.

. This assumption neglects thev effect of the voltlected herein forpurposes of clarification.

While there has been shown and; described what. is at 4presi-entconsidered. to be the preferred; embodiment oi`. the present invention,it will be:

obvious to those: skilled in the art thatvariatie:L modifications andsubstitutions' ot 'equivalents may be made therein. without departingfrom the 1 true scope ci. the inventionas defined. by the appendedclaims.

I clarin:

1. A, pulse-type'- povver supply.'- comprjsing an energy source, aninducta'nceivhich is periodically' linearly given an increment of.chargebythat source, a source ot substantially rectangular posi-.- tivepulses anda switching tube4 controlled by said.- A

begin to collapse, whereby there appears. across:

said inductance an oscillatory voltage, rneansin-h cluding anauto-transforrner connected to Said. anode. and utilizing'saidinductance as its primary for peakrectifying said voltage to deriveaunidirectional voltage, and capacitance effectively in parallel withsaid inductance to form a circuit resonatlng at a frequency Fzvequal tol-FiT' inwhich n is an integer less than 4, FL is the repetition rate ofthe rectangular pulses, and T isthetime during which the tube isconductive.

2. vA. pulse-type power supply comprising an energy source. aninductance which is periodically given an increment of charge by thatsource. a source of substantially rectangular pulses and au switchingtube controlled by said pulses, sald. tuba periodically interrupting theIiow of. current in.

1 said-inducta'nce as the tube. is rendered non-con.-

ductive at the termination of each pulse, thereby whereby there appearsacross said inductance. an. oscillatoryvoltage, means forpeak-rectifying said. voltage to derivev a unidirectional voltage, andcapacitance. effectively in parallel with said inl` ductance to form a4circuit resonating at a Irequency Frequal to A FL l 1-F1Z' in which` nisV an. integer not more thanflrll'r it the. repetition rate oftherectangular pulses, and; T is the time during which theptube iscmldwztive..

HANS C1. VSCHWARZ .References Cited in the lc of this patenia- UNITED-STATES PATENTS Date Number NameA 2,104,463 Johnson Jan. 4, 1938'2,157,534 George et a1'. May 9, 193g 2,352,299 lValker .Y,.... June 27,1944 2,424,972 ,Dubin n........ ..-e Aug.. 5, 1947. 2,435,414. Sziklaietal. Feb. 3, 1948 2,443,619 Hopper June 22, 1948 OTHER. REFERENCESPulse-Type High-Voltage Supply, by sieren and Kerkhof, Proceedings ofthe L R. E., March 194B; e

VOL 36. DD. lOl-A07.

